The present invention relates to a grease that exhibits good lubricating performance in a hot and high-vacuum environment. More particularly, the present invention relates to a lubricating grease that contains an alkyl substituted tetraphenylether as a base oil having incorporated therein bentonite as a thickener and at least one solid lubricant selected from the group consisting of molybdenum disulfide and tungsten disulfide.
The drive mechanism of machines that are to be used in a hot and high-vacuum atmosphere is composed of many mechanical elements such as gear wheels and bearings, and the use of lubricants is essential for smooth operation of these elements. To this end, solid lubricants typified by molybdenum disulfide are coated on the surface of metal parts to be used in a hot and high-vacuum atmosphere. In some cases, such solid lubricants are combined with soap-based greases containing petroleum lubes as base oils.
The use of solid lubricants alone has the problem that the lubricating film has a relatively weak adhesion to the substrate and is prone to separation in applications where high stresses are to be exerted. The combination of solid lubricants with soap-based greases that contain petroleum lubes as base oils has its own problems such as evaporation loss and deterioration loss, which result in the fouling of the interior of the machine in which the lubricant is used.
In order to solve the aforementioned problems, it is important that the lubricant to be used insure prolonged and consistent lubrication in a hot and high-vacuum atmosphere without experiencing any evaporation loss and deterioration loss, which would otherwise foul the interior of the machine in which the lubricant is used.